The present invention relates to a method and apparatus for connecting a ground power unit (GPU) to an aircraft. More particularly, the invention relates to a method and apparatus for connecting a towbarless tractor-mounted GPU to the aircraft using an intermediate cable and/or towbarless tractor which is configured to prevent the cable from being damaged by the wheels or clamping mechanism of the tractor as it is approaching and clamping onto the aircraft's nose landing gear.
GPU's are used to provide temporary power to an aircraft as it is parked, e.g., at an airport terminal gate. Prior art GPU's are typically stationary devices which are positioned, among other locations, adjacent the gate. Thus, when the aircraft is being towed from the gate to, e.g., a hangar, it must be disconnected from the GPU. As the aircraft is being towed, power for the aircraft is provided by the aircraft's auxiliary power unit (APU). However, APU's are relatively inefficient devices which consume a significant amount of fuel.
Towbarless tractors are used to tow aircraft. These tractors commonly comprise a horizontal U shaped frame which contains a clamping mechanism. The clamping mechanism clamps onto and lifts the aircraft's nose landing gear prior to towing. Thus, during the clamping operation the tractor is positioned so that the frame surrounds the front and both sides of the nose landing gear.
A towbarless tractor has been developed which includes an on-board GPU. Thus, the aircraft can be connected to the tractor-mounted GPU to provide power to the aircraft during the tow, which obviates the need to use the aircraft's inefficient APU.
To use the tractor-mounted GPU, an operator needs to connect the GPU cable to the aircraft's GPU receptacle. The GPU cable is a heavy electric cable which includes a connector on its free end that is configured to be inserted into the GPU receptacle. The GPU cable and connector are relatively heavy and require considerable force to be properly inserted into the receptacle.
The location of the GPU receptacle varies by type of aircraft, but is generally in the vicinity of the nose landing gear. Thus, to connect the GPU cable to the aircraft during or after the clamping operation, the operator often must climb onto the tractor and in some cases even step onto the clamping mechanism. Moreover, in the case of a tall aircraft the operator may have to stretch to reach the GPU receptacle, and in the case of a low aircraft the operator may have to crouch between the tractor and the aircraft fuselage to reach the GPU receptacle. In many cases climbing onto the tractor while handling the heavy GPU cable presents a fall hazard.
An alternative to climbing on the tractor to connect the GPU cable to the GPU receptacle is to stop the tractor short of the nose landing gear and connect the cable to the receptacle prior to the clamping operation. To do this the GPU cable has to be sufficiently long. However, a risk exists that such a long GPU cable may be run over or pinched or clamped by the clamping mechanism as the tractor approaches the nose landing gear. To avoid this risk a second operator must often be used to guide the cable; but this puts the operator at risk of being hit by the tractor or pinched by the clamping mechanism as the tractor approaches the nose landing gear.